Protective and alarm system



April 26, 1938. E. VROOM 2,115,152

PROTECTIVE AND ALARM SYSTEM Filed Nov. 15, 1936 I REPEA TEA N0. 2

REPEA TER INVENTOR 53 E. VROOM A T TORNEV Patented Apr. 26, 1938 UNITED STATES PATENT OFFICE PROTECTIVE AND ALARM SYSTEM Application November 13, 1936, Serial No. 110,615

6 Claims.

This invention relates to protective circuits and more particularly to a safety and alarm arrangement for telephone repeaters.

In the operation of thermionic repeaters from a common grid potential supply heretofore, one difficulty encountered has been the trouble occasioned by an inadvertent grounding of grid leads. To clear this it has been necessary to remove from service a group of repeaters, and test the several grid leads associated therewith to isolate the defective one. This required not only auxiliary repeaters for emergency use but also involved the loss of a repeater group for an extended period due to the considerable time consumed in hunting the nature and source of the trouble.

It is an object of this invention to provide an arrangement for thermionic repeaters operating from a common grid-potential supply that will quickly indicate a fault and its location.

In a preferred embodiment, the invention comprises copper-oxide rectifiers bridged across the grid impedances of the common grid-supply circuit. The rectifiers poled against the flow of grid current connect the grid leads, each of which embodies a. current-responsive means, and a common filament battery. An accidental ground occurring on a grid lead draws adequate current from the filament battery to actuate the currentresponsive means. This operates a signaling circuit which includes an audible alarm and an indicator showing the nature and location of the trouble.

The invention will be readily understood from the following description taken together with the accompanying drawing which is a circuit diagram showing the invention employed with a plurality of repeaters.

The drawing is a portion of the system for energizing and testing repeaters disclosed in the patent of E. Vroom No. 1,616,156, issued February 1, 1927.

Referring to the drawing, repeater No. I is represented as comprising electron discharge devices ill and II, each of which includes a control grid and a cathode, input transformers I2 and I3, and output transformers l4 and I5. Cathode heating current is supplied from a common 24- volt battery I6 which has its negative terminal connected to a negative bus-bar I1 and its positive terminal ,to ground.

Grid potential is obtained from a common grid-supply circuit comprising a 10-volt grid battery l8, impedances 23 and 24, milliammeter 25, and rheostat 26. A link 2! joins the positive terminal of impedance 23 and the negative busbar ll. Potentials developed across the impedances 23 and 24 are supplied over leads 28 and 29, respectively, to the grids of the electron discharge devices. Normally, no current flows on 5 these leads.

Milliammeter 25 serves to indicate the magnitude of current flowing through impedances 23 and 24. It is understood that this current is to be maintained at a predetermined value so that 10 substantially constant potentials will be produced across the impedances 23 and 24. A more detailed description of the circuit including the requisite regulatory apparatus may be had by referring to the Vroom patent, supra.

In a preferred embodiment of this invention, copper-oxide rectifiers 34 and 35 are bridged across the impedances 23 and 24, respectively. The rectifiers are so poled that normally no cur' rent from grid battery 18 will flow therethrough. The number of rectifiers included in each bridge will depend on' the operating conditions for a particular circuit. It is understood that other means restricting current flow to one direction may be substituted for the copper-oxide rectifiers.

Fuses 36, 36 connected in the grid leads 28 and 29 are of a type disclosed in the patent of M. C. Rorty et al. No. 761,916, issued June '7, 1904. Each of these comprises a terminal 31 and a tongue 38 flexed by a fuse-link 39. The tongue 38, when retracted due to a rupture of the fuselink 39, is adapted to engage contact 40. The contacts 40, 40 of the two fuses 36, 36 are connected by a lead 45 to one terminal of the winding of an alarm relay 46. The opposite terminal of this winding is connected to battery 41. Relay 46 is normally unoperated, hence its associated contacts are normally open. It is understood that a relay or circuit breaker having a relatively low alternating current impedance, or similar current-responsive device, may be substituted for the fuses 36, 36.

Contact 48 is connected through a key 49 to ground 50, and contact 5| is connected through a signal lamp 52 to battery 53. Both of these contacts are associated with armature 54 which is directly joined to the lead 45. Contacts 55 and 56 are connected through a lamp 5'! and a bell 58, respectively, to the battery 53. These contacts are associated with armatures 60 and-6|, both of which are grounded at 62.

In operation, let it be assumed that an accidental ground indicated at 63 occurs on lead 29. Current Will fiow from cathode battery; 16 through ground 63, tongue 38, fuse-link 39, ter

' with the .contacts and 56, respectively. This energizesfthe alarm bell 58 and the filament of lamp 5! through circuits comprising ground 62,

minal 31, lead 29, mamas '35 and 34, link 21, m the common negative bus-bar l1. Adequate currentwill flow in this'circuit to burn-out the:

fuse link 39. This causes the flexed tongue 38 to retractsufiiciently to engage contact 40.

Acircuit is now established to energize relay 46. 40, lead, 45, winding of relay 46,,and battery 41.

Relay 46 operates, thereby actuating armature 7 Relay 46 is locked up by a'circuit consisting of battery 41, Winding of relay 46, armature 54, contact 48, key 49, andground 50. At'th'esame time, thefila- 54.170 close, the contacts 48 and 5|.

ment of signal lamp 52 is energized by 'a circuit including battery 53, filament of lamp 52,, closed contact 51, key 49, and. ground 50.j Signal lamp; '52 indicates that the ground occurredfon' re peaterNoul." '1 Also, when alarmrelay 46 is operated,.the armatures and'6l are actuated into engagement the respective contacts associated with the armatures 60. andiGl, lead 83;. and battery 53.

r 56' ringsto call attention to the occurrence of a troublewhilethe lamp 5'l indicatesthat the trouble involves the grid lead of arepeater. As previously pointed out,'lamp 52 identifies theparticular repeater, or group of repeaters as the case maybe, on which the fault occurred.

As.shown in the drawing, lamp 52 is connected to indicate a groundfon' either gridlead 28 or 29 ofirepeater No. I. The blown fuse will indicate the particular lead of these two on which the 1 ground occurred. .It isobviousthat-the circuit 'may'be so designed that "relay 4fi andan indi eating lamp-52 would beindividual to each grid a relay becomes'deenergized'andithe signaling .c'irlead.

When a ground shown at 64occurs on'the grid I lead Z8, the operation of the signaling circuit will be the same as that aforedescribed in response toasimilar fault on gridlead 29.

.After the ground is cleared. and the burnt-out fuse is replaced, key 49 is operated, to interrupt the locking circuit for relay 46. Thereupon, this cuit controlled thereby is returned to normal.

J It is further seen in the drawingthat leads l6 and 1 l j connected to the common grid-supply circuitjat the points]? and 13, respectively'fare 7 utilized to energizethecontrol' grids of repeater 7 'No. 2. Itis understood that the lattercomprises the same'apparatus shown and described. above in connection with repeaterNo; l. It'is alsoevident :that the gridsof additional repeaters'may be energizedyfrom the common grid supply circuit by a tapping their respective leads to the points 12 and'l3'. r V Currentresponsive devices 14, Hembodied'in the grid leads '10 and H are duplicates of the devices ,36, 36 both with regard to their; structure and operation. Therefore, an inadvertent ground out and operate, thereby completing'an energi-Q is 'connectedtobattery 16. This relayoperates;

occurring on either grid lead :10 or;1l will cause the respective current responsivejdevice to burn- ZatiOn -circuit :for. alarm relay 215 whose winding and locksup' through" ajcircuit" comprising battery 16,; winding. of relay15, armature '11; contact 18, key l9,-and ground 80.

.Since'contactlll is now closed, the filament of :signallamp 82-is energized in a circuit including .battery53,l ead 83, the filament of lamp 82, contacti8l,-key 19,-and ground 80. Signal lamp 82 This comprises ground 63, tongue 38, contact Bell 7 indicates that the accidental ground occurred on one of the two grid leads associated withrepeater No. 2. The blown fuse isolates the particular one of these two on which the accidental ground occurred.

Also, the operation of-alarm relay 'l5 effects the closing of contacts 84 and 85'to establish energization circuits for the common signal lamp ,5!

'- and the common alarmubell 58. The energization circuitfor the signal lamp 57 includes ground 86, closed contact 85, lead 81, the filament of lamp I 51; lead 83, and battery 53. Thefenergization circuit for the alarmbell 58 embodiesgroundtfi;

closedcontact 84, lead 88,,bell '58, lead 83, and

battery 53. a

Thus, again, bell 58 announces the occurrence of a fault while the lamp 5'! indicates the latter as involving the grid leads of one of several re-f peaters. As pr eviouslypointed out, signal lampsf] 52 and 82 identify. the particular repeater on 'Whichthefault occurred. 'After tl' e'blowneout fuse I4 is replaced and the accidental ground. is removed from the grid lead'lfl or H the signaling circuit associated with repeater No. 2 isrestored to normal by deenergizing the alarm relay l5.

This'is accomplished by operating the key ieto' interrupt the holding circuit for this relay The number of repeaters included ina group energized from the oommon-grid-supply circuit v is, of course, determined by the efficiency at which itis desired to operate the individual repeatersi Inasmuchas the number may, in some cases, ex-.

ceed two, it is obvious that-the signaling circuit 7 can be readily adapted to accommodate any numa ber of repeaters. In this connection each repeater may have its individual signal lampand,

in addition, be operatively connected with the commonsignal lamp 5l and the common alarm bell 58.

In the event of operating the repeaters in connaling circuit associated with'th'e repeaters lends junction withia telephone central oliice, the sigitself readily for combination with the central f ofiicealarm apparatus. Thus, the common alarm bell 58 may become the all-purpose alarm. of. the central office, and theccmmon lamp 51 may be incorporated as indicating. one type of fault in a group indicator- The :latter may be a drop, or other suitable type, many of which are wellknown in telephone practice. The individual signal .lamps should, of course, be lccatedas close to, r

the repeaters as local conditions will permit; "A

preferred location would be the relay which the repeaters are mounted. r

It is understood that the signaling circuit illus- "trates one simple formand further, that other signaling apparatus may be substituted if desired-Q Furthermore, it is apparent that'the signaling cir- V cuit maybe modified in a-manner that eliminates; "the individual 1amps 52, and 82, and utilizes, only the general larnp551; In thisevent, the' blown fuse would identify the particular gridlead-andf in addition, the" repeater on which the ground occurred.

What is claimed is:

potential circuit'comprising a source of current and an impedance, a source or, currentfor energ giz'ing" the cathode, a leadconnectingthegiml. Incombinat'ion, anelectron'discharge device; f "including af'conftrol grid-jand a cathode, agrid current-res 'aonsive[means in the lead connecting 1 the impedance and control grid to efiect an interruption thereof.

2. A combination according to claim 1 in which the bridging means is a copper-oxide rectifier poled against the source of current flowing in the grid-potential circuit.

3. In combination, an electron discharge device including a control grid and a cathode, a gridpotential circuit including a source of current and an impedance, a source of current for energizing the cathode, a lead joining the impedance and control grid, a copper-oxide rectifier bridged across the impedance and poled against the current in the grid-potential circuit for connecting the grid lead and the cathode source of current,

current-responsive means for interrupting the grid lead, and signal means responding to the interruption for announcing its occurrence.

4. In combination, in a repeater comprising a pair of electron discharge devices each of which includes a control grid and a cathode, a common grid circuit embodying a source of current and a plurality of impedances, a common source of current for energizing the cathodes, leads connecting the impedances and the control grids, means bridging the impedances and restricting current flow therethrough to one direction for joining the control-grid leads and. the cathode source of current, and means responsive to current in the control-grid leads for disconnecting the control grids from the impedances.

5. A combination according to claim 4 in which the bridging means are copper-oxide rectifiers, and which includes a signalingmeans associated with the control-grid leads and operatively responsive to the interruption for indicating its occurrence.

6. In combination, a plurality of repeaters each each of the latter including a control grid and cathode, a common grid circuit embodying a source of current and a plurality of impedances, a common source of current for energizing the cathode, leads connecting the impedances and the control grids of the repeaters, a copper-oxide rectifier bridging each impedance and poled against the flow of current in the common grid circuit for connecting the control-grid leads tothe cathode source of current, means in each control-grid lead to respond to current flow therein for disconnecting the respective grid leads from the common grid circuit, and signaling means operatively responsive to the interruption for announcing the occurrence of the latter and identifying the repeater on which it happened.

EDWARD VROOM.

' comprising a pair of electron discharge devices, 

